Strain-responsive regions in the platelet-derived growth factor-A gene promoter.
Proliferation of cultured neonatal vascular smooth muscle (VSM) cells is enhanced by exposure to cyclic mechanical strain, in part through autocrine action of secreted platelet-derived growth factor (PDGF). We examined transcription factors and DNA response elements that may participate in the induction of PDGF-A gene transcription by mechanical strain. PDGF-A mRNA increased gradually over 4 to 24 hours exposure to cyclic (1 Hz) strain. This was due, at least in part, to increased transcription since a full length (890 bp) PDGF-A promoter reporter construct was induced 3.5-fold in transfected VSM cells exposed to strain for 24 hours. A series of PDGF-A promoter truncation reporter constructs was used to identify potential regions of the promoter involved in regulation by strain. Strain-responsive regions were found between -262 bp and -92 bp and between -92 bp and -41 bp of the promoter. Since these regions are GC-rich and contain response elements for Egr-1 and Sp-1, we examined expression of these transcription factors in response to strain. mRNA for both factors increased over 0.5 to 4 hours of strain, while protein expression for both increased gradually over a 24 hours period. Gel shift assays with a probe specific for Egr-1 demonstrated at least 1 prominent new shifted band after 4 to 12 hours exposure to strain. An Sp-1 probe demonstrated constitutive shifted bands that did not change in response to strain. Thus, GC-rich regions in the proximal 92 bp of the PDGF-A promoter contain mechanical strain-responsive elements that bind Egr-1 and possibly Sp-1.
Wilson
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Cardiovascular Research Institute, Division of Nephrology, University of California, San Francisco 94143, USA.
Vives
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F
Collins
T
T
Ives
H E
HE
D000818:Animals; D000831:Animals, Newborn; D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D051766:Early Growth Response Protein 1; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D017874:Immediate-Early Proteins; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis* / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016329:Sp1 Transcription Factor / Q000096:biosynthesis; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D010982:Platelet-Derived Growth Factor; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; C075278:platelet-derived growth factor A